1. Technical Field
The present invention relates to a semiconductor device and a method of manufacturing a semiconductor device.
2. Related Art
In the conventional art, etching is performed on a semiconductor substrate to form a trench in the semiconductor substrate and an epitaxial layer is further formed in the trench (see, for example, Japanese Patent Application Publications Nos. 2005-32792, 59-69943, and 2007-329385. Furthermore, it is known to provide a field oxide film in a semiconductor substrate in a surrounding portion adjacent to an active portion (for example, see Japanese Patent Application Publication No. 5-55262) and to provide a LOCOS isolation region in a semiconductor substrate (see, for example, Japanese Patent Application Publication No. 1-246844).
When the impurity concentration of the semiconductor layer in which the trench is formed by the etching is comparable to that of the epitaxial layer that is further formed in the trench, electrical fields can concentrate on the bottom of the trench.